Vitamin A

Vitamin A, also known as retinol, is a fat soluble vitamin that comes in two forms: preformed and provitamin A carotenoid. The first is found in foods originating from animals such as liver, whole milk and fortified food products. It is absorbed as retinol but is later converted into retinal and retinoic acid by the body. However, provitamin A carotenoid is absorbed from foods originating from plants such as fruits and vegetables. This is then converted into retinol. There are currently 563 known carotenoids, however less than ten percent of them can be converted into Vitamin A once in the body. Nevertheless, there are three main carotenoids that are found in plants; beta-carotene, alpha-carotene and beta-crytoxanthin. Retinol is commonly found in animal products such as milk, butter, egg yolk and liver and in plant products such as dark green leafy vegetables, fruits, broccoli and carrots. More information is given in the table below.

 

Table 1: Selected animal sources of vitamin A [18]

Food

Vitamin A (IU)*

%DV**

Liver, beef, cooked, 3 ounces

27,185

545

Liver, chicken, cooked, 3 ounces

12,325

245

Milk, fortified skim, 1 cup

500

10

Cheese, cheddar, 1 ounce

284

6

Milk, whole (3.25% fat), 1 cup

249

5

Egg substitute, ¼ cup

226

5



Table 2: Selected plant sources of Retinol (from beta-carotene) [18
]

Food

Vitamin A (IU)*

%DV**

Carrot juice, canned, ½ cup

22,567

450

Carrots, boiled, ½ cup slices

13,418

270

Spinach, frozen, boiled, ½ cup

11,458

230

Kale, frozen, boiled, ½ cup

9,558

190

Carrots, 1 raw (7½ inches)

8,666

175

Vegetable soup, canned, chunky, ready-to-serve, 1 cup

5,820

115

Cantaloupe, 1 cup cubes

5,411

110

Spinach, raw, 1 cup

2,813

55

Apricots with skin, juice pack, ½ cup

2,063

40

Apricot nectar, canned, ½ cup

1,651

35

Papaya, 1 cup cubes

1,532

30

Mango, 1 cup sliced

1,262

25

Oatmeal, instant, fortified, plain, prepared with water, 1 cup

1,252

25

Peas, frozen, boiled, ½ cup

1,050

20

Tomato juice, canned, 6 ounces

819

15

Peaches, canned, juice pack, ½ cup halves or slices

473

10

Peach, 1 medium

319

6

Pepper, sweet, red, raw, 1 ring (3 inches diameter by ¼ inch thick)

313

6

Source: http://dietary-supplements.info.nih.gov/factsheets/vitamina.asp

Vitamin A has many functions. Firstly, it is known for improving eye sight, particularly in the dark by allowing the retina to adapt to darkness. However, it also helps regulate and strengthen the immune system. Furthermore, it helps our bodies protect themselves by building up mucous membranes in areas such as the throat, nose and lungs which act as barriers. This vitamin also promotes healthy bone growth, cell division, reproduction, cell differentiation, healthy surface linings of the eyes, and healthy respiratory, intestinal and urinary tracts. By maintaining the health of these various organ systems, it becomes more difficult for bacteria to enter our bodies and cause infection. Therefore, this vitamin is essential for our health. Furthermore, it protects us against air pollutants and is involved in the synthesis of certain hormones such as progesterone.

Because it is an antioxidant, Retinol has various anti-ageing properties such as the prevention of damage to cells and wrinkles. It has also been shown to delay the onset of senility and promote healthy digestion. It is also one of the main ingredients in many topical skin creams as retinol and retinoid enhance skin cell replacement. Furthermore, this vitamin has been shows to increase collagen levels along with skin elasticity and stretch ability. These factors combined lead to smooth skin, fewer wrinkles and fine lines and reduction of bad pigmentation and acne.

Despite Retinol’s multiple benefits, it is known for making skin more sensitive to sunlight. This increases the risk of damaging the skin cells when exposed to the sun. However, this can be counterbalanced by applying sunscreen in generous quantities when being exposed to the sun.

Symptoms of Vitamin A overdose include:

  • Joint pain
  • Cracked lips
  • Dry and itchy skin
  • Nausea and vomiting
  • Weight loss

Meanwhile, symptoms of Vitamin Deficiency include:

  • night blindness
  • increased susceptibility to infection
  • rough, dry scaly skin
  • loss of smell and appetite
  • frequent fatigue
  • lack of tears
  • defective teeth and gums
  • retarded growth
  • keratinisation of the epithelial tissues in the nasal and respiratory passages


In order to avoid any of these symptoms, it is recommended that we ingest only 900 RE (retinol equivalents) per day.


TOP Vitamin A
BACK to A-Z-Vitamins
HOME to Age-well





New! Comments

Have your say about what you just read! Leave me a comment in the box below.

Translate this Site


Search This Site

Loading


Follow this Great site on healthy aging and preventing age-related disease: http://www.age-wel.org

Subscribe to E-Zine

Enter your E-mail Address
Enter your First Name (optional)
Then

Don't worry — your e-mail address is totally secure.
I promise to use it only to send you Age Well Newsletter.



Support this Site


If you want to support age-well.org, without it costing you a cent, shop at AMAZON st the link below.


The site age-well.org is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com.


Holiday Specials

For Holiday Specials at Amazon, Click Here


Active? Try the Dr Weil Vitamin Advisor